Single-crystalline silicon essential for the production of devices such as semiconductor devices is grown as a crystal by the CZ method and the FZ method, and a polycrystalline silicon rod or a polycrystalline silicon block is used as the raw materials in such a case. Such a polycrystalline silicon material is produced in many cases by the Siemens method (see, for example, Patent Literature 1). The Siemens method is a method in which by bringing a gas of a silane raw material such as trichlorosilane or monosilane into contact with a heated silicon core wire, polycrystalline silicon is grown in the vapor phase (deposited) on the surface of the silicon core wire by the CVD (Chemical Vapor Deposition) method.
For example, when single-crystalline silicon is crystal-grown by the CZ method, a polycrystalline silicon block is charged in a quartz crucible and heated to be melted, a seed crystal is dipped in the resulting silicon melt to extinguish dislocation lines to be made free from dislocation, and then the crystal pulling up is performed while the crystal diameter is being slowly expanded until the diameter of the crystal reaches a predetermined diameter. In this case, when unmelted polycrystalline silicon remains in the silicon melt, the unmelted polycrystalline pieces drift in the vicinity of the solid-liquid interface by convection to induce the generation of dislocation, and thus the polycrystalline silicon remaining unmelted causes the crystal line to be extinguished.